Mechanical & Drives
Spur gear dimensions (module) calculator
Pitch, outside and root diameters and centre distance from module and teeth.
Calculating…
How it's calculated
Pitch diameter = m × z
Outside diameter = m × (z + 2)
Root diameter = m × (z − 2.5)
Centre distance = m × (z1 + z2) ÷ 2
DP = 25.4 ÷ m
To identify an unknown metric gear, measure the outside diameter and count the teeth: module ≈ OD ÷ (teeth + 2). Gears must share the same module (or DP) and pressure angle to mesh.